/*
 * Alloy Analyzer
 * Copyright (c) 2002 Massachusetts Institute of Technology
 *
 * The Alloy Analyzer is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * The Alloy Analyzer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with the Alloy Analyzer; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package alloy.ast;

/**
   Represents an if-then-else expression.
*/

final public class IfThenElseExpr extends TypedExpr {

    private static final int IF_FORMULA_INDEX = 0;

    private static final int THEN_EXPR_INDEX = 1;

    private static final int ELSE_EXPR_INDEX = 2;

    public IfThenElseExpr(Location location_, Formula ifFormula_, Expr thenExpr_, Expr elseExpr_) {
        super(location_, ifFormula_, thenExpr_, elseExpr_);
    }

    public IfThenElseExpr(Formula ifFormula_, Expr thenExpr_, Expr elseExpr_) {
        this(Location.UNKNOWN, ifFormula_, thenExpr_, elseExpr_);
    }

    public Formula getIfFormula() {
        return (Formula)childAt(IF_FORMULA_INDEX);
    }

    /** set the IfFormula of this */
    public void setIfFormula(Formula newChild_) {
        setChild(IF_FORMULA_INDEX, newChild_);
    }

    public Expr getThenExpr() {
        return (Expr)childAt(THEN_EXPR_INDEX);
    }

    /** set the ThenExpr of this */
    public void setThenExpr(Expr newChild_) {
        setChild(THEN_EXPR_INDEX, newChild_);
    }

    public Expr getElseExpr() {
        return (Expr)childAt(ELSE_EXPR_INDEX);
    }

    /** set the ElseExpr of this */
    public void setElseExpr(Expr newChild_) {
        setChild(ELSE_EXPR_INDEX, newChild_);
    }

    public String nodeString() {
        return "if " + getIfFormula().nodeString() + " then " +
        getThenExpr().nodeString() + " else " + getElseExpr().nodeString();
    }
    
    /**
     * accept an AST visitor
     * @param visitor_ the visitor
     */
    protected void acceptVisitor(ASTVisitor visitor_) {
        visitor_.visit(this);
    }

    /**
     * accept a returning AST visitor
     * @param visitor_ the visitor
     * @return the Object returned by the visitor
     */
    protected Object acceptReturnVisitor(ASTReturnVisitor visitor_) {
        return visitor_.visit(this);
    }

    
}
       
   
